1. Field of the Invention
The present invention relates to an electron beam generating apparatus including electron emission devices, an image display apparatus using this electron beam generating apparatus, and a method of driving these apparatuses.
2. Related Background Art
Thermionic cathodes and cold cathodes are conventionally known as electron emission devices. As cold cathodes, a field emission device (to be abbreviated as an FE device hereinafter), a metal/insulator/metal emission device (to be abbreviated as an MIM device hereinafter), and a surface conduction electron emitting device are known.
Known examples of the FE device are W. P. Dyke & W. W. Dolan, "Field emission", Advance in Electron Physics,. 8, 89 (1956) and C. A. Spindt, "Physical properties of thin-film field emission cathodes with molybdenium cones", J. Appl. Phys., 47, 5248 (1976).
One known example of the MIM device is C. A. Mead, "Operation of tunnel-emission devices", J. Appl. Phys., 32, 646 (1961).
As the surface conduction electron emitting device, M. I. Elinson, Radio Eng. Electron Phys., 10, 1290 (1965) and other devices to be described later are known.
The surface conduction electron emitting device uses a phenomenon in which electron emission is caused by flowing a current parallel to the surface of a thin film with a small area which is formed on a substrate. Among the surface conduction electron emitting devices that have been reported, in addition to the above-mentioned device by Elinson et al. which uses a thin SnO.sub.2 film, are a device using a thin Au film [G. Dittmer: "Thin Solid Films", 9 317 (1972)], a device using a thin In.sub.2 O.sub.3 /SnO.sub.2 film [M. Hartwell and C. G. Fonstad: "IEEE Trans ED Conf", 519 (1975)], and a device using a thin carbon film [Hisashi Araki et al.: Vacuum, Vol. 26, No. 1, 22 (1983)].
FIG. 23 is a plan view showing the device by M. Hartwell described above, as a typical example of the device structures of these surface conduction electron emitting devices. Referring to FIG. 23, reference numeral 3001 denotes a substrate; and 3004, a thin conductive film of a metal oxide formed by sputtering. As in FIG. 23, the thin conductive film 3004 is so formed as to have an H-like planar shape. On the thin conductive film 3004, an electron emission portion 3005 is formed by electro-processing called "energization forming" (to be described below). In FIG. 23, a distance L is set at 0.5 to 1 [mm], and W is set at 0.1 [mm]. Note that in FIG. 23, the electron emission portion 3005 is illustrated as a rectangular portion in the center of the thin conductive film 3004 for convenience, but this is merely a schematic illustration of that portion. That is, the position and shape of an actual electron emission portion are not precisely depicted in FIG. 23.
In the above surface conduction electron emitting devices represented by the device by M. Hartwell et al., it is the general approach to form the electron emission portion 3005 by performing electro-processing called energization forming for the thin conductive film 3004 prior to causing electron emission. The energization forming is the processing in which a constant DC voltage or a DC voltage which rises very slowly, e.g., at a rate of 1 V/min is applied across the thin conductive film 3004 to locally destroy, deform, or modify the thin conductive film 3004, thereby forming the electron emission portion 3005 in an electrically high-resistance state. Note that a fissure is formed in a portion of the thin conductive film 3004 which is locally destroyed, deformed, or modified. Electron emission is performed near this fissure upon application of an appropriate voltage to the thin conductive film 3004 after the energization forming.
The surface conduction electron emitting device described above is simple in structure and easy to fabricate. The result is that a large number of devices can be formed across a large area. For this reason, a method of driving an array of a number of these devices is being studied as disclosed in, e.g., Japanese Patent Laid-Open No. 64-31332 filed by the present applicant.
Also, for applications of the surface conduction electron emitting devices, studies have been made on, e.g., image forming apparatuses, such as image display apparatuses and image recording apparatuses, and charged beam sources. In particular, as an application of the surface conduction electron emitting device to an image display apparatus, an image display apparatus making use of a combination of the device and a phosphor which luminesces when irradiated with an electron beam is being studied, as disclosed in, e.g., U.S. Pat. No. 5,185,554 or Japanese Patent Laid-Open No. 2-257551 filed by the present applicant. These image display apparatuses using the combination of the surface conduction electron emitting device and a phosphor are expected to provide better characteristics than those obtained by conventional image display apparatuses of other types. For example, image display apparatuses of this type can be said to be superior to liquid crystal displays that have become popular in recent years, in that these apparatuses require no back light because they are of a self-luminescing type and have a wide viewing angle.